abstracts: geology 159 



discussed in detail and formulas are presented to facilitate the evalua- 

 tion and classification of waters with respect to these tendencies in qual- 

 ity. H. S. 



GEOLOGY. — Potash-bearing rocks of the Leucite Hills, Sweetwater 

 County, Wyoming. Alfred R. Schultz and Whitman Cross. 

 Bulletin U. S. Geological Survey, No. 512, p. 1 to 39, with maps. 



The Rock Springs district in Sweetwater County, Wyoming, consists 

 structurally of a low anticlinal dome of Cretaceous and Tertiary rocks 

 plunging to the north and to the south. The major north-south axis 

 is approximately 90 miles long and the width of the dome is about 50 

 miles. The beds on the west side of the anticline dip from 5° to 10°. 

 From the central part of the dome have been removed all of the Ter- 

 tiary Green River and Wasatch beds, the late Cretaceous ("Laramie"), 

 and part of the Montana formations. 



Resting on or cutting thru the sedimentary rocks in the north half of 

 this dome are the Leucite Hills, composed of leucite-bearing lavas rich 

 in potash. These lavas are certainly younger than the Green River beds 

 and were presumably poured out on the more or less level plain upon 

 which the Bishop conglomerate was deposited. The masses of leucite- 

 bearing rock occur as dikes, sills, sheets, stocks and surface flows and rest 

 upon or come in contact with Green River, Wasatch, "Laramie" and 

 various formations of Montana age. 



The lavas of the Leucite Hills contain on the average a larger per- 

 centage of potash than any other known igneous rocks. However, 

 the extraction of the entire potash content of these rocks must be effected 

 by a process applicable to leucite, sanidine, and phlogopite at least, and 

 probably to other minerals, as the potash in the leucite-bearing rocks 

 occurs in each of the above mentioned minerals. A. R. S. 



GEOLOGY.— The granites of Connecticut. T. N. Dale and H. E. 

 Gregory. Bulletin U. S. Geological Survey No. 484. Pp. 137, 

 with colored geologic map, 4 text maps, 8 figs., 6 pis. 1911. 

 To Part I, Gregory contributes a brief outline of the geology and 

 geologic history of the State with brief descriptions of granite, granite- 

 gneiss, pegmatite, porphyry, also paragraphs on granitic intrusions and 

 the age of Connecticut granites and granite-gneisses which, with the 

 exception of the Becket Gneiss, are regarded as post-Carboniferous. 

 Dale has in the same part 18 pages on the structure, variation, discolora- 

 tion, decomposition of granite, repeated from his previous granite bulle- 

 tins, and a few observations on micro-structure, flow, inclusions, plicated 



